Hybrid hydrogels of porous graphene and nickel hydroxide as advanced supercapacitor materials

Abstract

Graphene-based hydrogels can be used as supercapacitor electrodes because of their excellent conductivity, their large surface area and their high compatibility with electrolytes. Nevertheless, the large aspect ratio of graphene sheets limits the kinetics of processes occurring in the electrode of supercapacitors. In this study, we have introduced in-plane and out-of-plane pores into a graphene–nickel hydroxide (Ni(OH)₂) hybrid hydrogel, which facilitates charge and ion transport in the electrode. Due to its optimised chemistry and architecture, the hybrid electrode demonstrates excellent electrochemical properties with a combination of high charge storage capacitance, fast rate capability and stable cycling performance. Remarkably, the Ni(OH)₂ in the hybrid contributes a capacitance as high as 3138.5 F g⁻¹, which is comparable to its theoretical capacitance, suggesting that such structure facilitates effectively charge-transfer reactions in electrodes. This work provides a facile pathway for tailoring the porosity of graphene-based materials for improved performances. Moreover, this work has also furthered our understanding in the effect of pore and hydrogel structures on the electrochemical properties of materials.